Physical properties:

The physical properties of the fuel material are primarily of interest in ensuring its integrity in during the manufacturing process. Nevertheless they must be considered within assessments of the integrity of the core under operating conditions and the conditions of hypothetical accidents. A physical and mechanical property should also allow economical manufacturing. The fuel material should have a low coefficient of expansion.

It is impossible to fabricate classical refractory ceramics to 100 percent of their theoretical density. Thus, methods of controlling the porosity of the last product must be considered. A role of this initial porosity as sites for fission gas, as well as its belongings on thermal conductivity and mechanical strength, is an important factor in the design.